Renal sinus cyst

Renal sinus cysts are simple renal cysts that lie within the renal sinus.

They can be subdivided into :

• parapelvic cysts: originate from the adjacent parenchyma and protrude into the renal sinus
• peripelvic cyst: originate within the sinus itself and have a lymphatic origin

Peripelvic cysts are frequently bilateral. They appear as water attenuation cysts closely abutting the pelvis & infundibuli, rarely cause functional renal derangement by compression. When followed up they remain unchanged in size. They may be confused with hydronephrosis on NECT and USG, but on CECT the differentiation is obvious.

Parapelvic cysts are simple renal cysts that plunge into the renal sinus from the adjacent renal parenchyma. They are usually single or few and resemble simple renal cortical cyst in morphology. A parapelvic cyst at times may cause compression of the pelvicalyceal system resulting into hydronephrosis.